In recent years, three-dimensional mounting technology is drawing attention as a method for integrating semiconductor devices. As one of the three-dimensional mounting technology, there is a method of three-dimensionally stacking substrates by forming a deep hole in a substrate on which an integrated circuit is formed, stacking such substrates on top of each other in a vertical direction, and forming a wiring with copper or the like inside the deep hole, so that a degree of integration can be increased. In forming the deep hole, the speed and the cost in which the deep hole is formed are important.
One known method forms a deep hole in a substrate by providing a resist pattern having an opening part corresponding to the deep hole (photoresist film including an opening part) on a substrate on which an integrated circuit is formed, and performing plasma etching on the substrate using the resist pattern as a mask. The resist pattern is formed by forming a photoresist film by applying photoresist, and exposing/developing the photoresist film. In a case of etching a substrate on which a photoresist film including an opening part is formed, a deep hole is formed by repeating a step of forming a hole by etching and a step of depositing polymer by polymerization. This method is known as the so-called “bosch process” (see, for example, Patent Document 1). In the etching step, a mixed gas including SF6 gas and Ar gas is used for forming the hole. In the polymerization step, polymer is deposited to an inner wall of the hole and a substrate surface by using a mixed gas including CHF3 gas and Ar gas.